(1) Field of the Invention
The instant invention relates to wireless telecommunication (T/C) systems. More specifically, the invention relates to a wireless T/C antenna mounts.
(2) Description of Related Art
Over the last 20 years, the use of cellular phones as a primary means of communication has exploded worldwide. In order to provide coverage area and bandwidth for the millions of cell phones in use, there has also been a huge increase in the number of TIC transmitter/receiver antenna installations (T/C installations) and the number of T/C transmitter/receiver antennas (antennas) mounted on those TIC installations. In most cases, the antennas are mounted on towers, monopoles, smokestacks, buildings, poles or other high structures to provide good signal propagation and coverage. There are literally hundreds of thousands of T/C installations in the U.S., with each installation carrying multiple antennas from multiple carriers.
Referring to FIGS. 1-3, each tower or installation 10 has an associated base station 12, which includes power supplies, radio equipment, interfaces with conventional wire and/or fiber optic TIC system nodes 14, microwave links, etc. The base station node(s) 14, in turn, have a wireless or wired connection to each carrier's Network Operations Center (NOC) 16 to monitor and control the transmission of T/C signals to and from the antennas 18 and over the carrier's network.
At each tower installation, each carrier will typically have three separate antennas 18 oriented 120° apart to serve three operational sectors of its service area. However, it should be noted that many other types of installations may have only a single antenna 18. For example, antennas 18 mounted on the sides of building are typically pointed in a single direction to provide coverage in a particular direction, i.e. towards a highway.
Each antenna 18 is typically mounted on a vertical pole 20 using a mount 22 having some ability to manually adjust the orientation (azimuth and tilt) of the antenna 18 relative to the desired service area. Typical manual adjustment of tilt, or downtilt position (angular direction around a horizontal pivot axis) involves manually tilting the antenna 18 downward using a mechanical downtilt bracket 21 (usually provided as part of the mount) and clamping or tightening the tilt bracket 21 in the desired position (FIGS. 2A and 2B). Typical manual adjustment of an azimuth position (angular direction around a vertical axis) involves manually rotating the mount 21 around the vertical pole 20 and physically clamping the mount 21 in the desired position (FIGS. 2C and 2D).
When a carrier designs a service coverage area, they will specify the desired azimuth and tilt angles of the antennas 18 that they believe will provide the best service coverage area for that installation 10. Antenna installers will climb the tower or building and install the antennas 18 to the provider's specifications. Operational testing is completed and the antenna mounts 21 are physically clamped down into final fixed positions. However, various environmental factors often affect the operation of the antennas 18, and adjustments are often necessary. RF interference, construction of new buildings in the area, tree growth, etc. are all issues that affect the operation of an antenna 18. Additionally, the growth of surrounding population areas often increases or shifts signal traffic within a service area requiring adjustments to the RF service design for a particular installation. Further adjustment of the antennas 18 involves sending a maintenance team back to the site to again climb the tower or building and manually adjust the physical orientation of the antenna(s) 18. As can be appreciated, climbing towers and buildings is a dangerous job and creates a tremendous expense for the carriers to make repeated adjustments to coverage area.
As a partial solution to adjusting the vertical downtilt of an antenna 18, newer antennas may include an internal “electrical” tilt adjustment which electrically shifts the signal phase of internal elements (not shown) of the antenna 18 to thereby adjust the tilt angle of the signal lobe (and in some cases reduce sidelobe overlap with other antennas) without manually adjusting the physical azimuth or tilt of the antenna 18. This internal tilt adjustment is accomplished by mounting internal antenna elements on a movable backplane and adjusting the backplane with an antenna control unit (ACU) 24 which integrated and controlled through a standard antenna interface protocol known as AISG (Antenna Interface Standards Group). Referring to FIG. 3, the antennas 18 are connected to the local node through amplifiers 26 (TMA—tower mounted amplifiers). A local CNI (control network interface) 28 controls the TMAs 26 and ACUs 24 by mixing the AISG control signal with the RF signal through bias T connectors 30. Each carrier uses the AISG protocols to monitor and control various components within the TIC system from antenna to ground. Antenna maintenance crews can control the antennas 18 from the local CNI 28 at the base station 12 and, more importantly, the carrier NOC 16 has the ability to see the various components in the signal path and to monitor and control operation through the AISG protocols and software.
While this limited phase shift control is somewhat effective, it is not a complete solution since adjustment of the signal phase of the internal antenna elements often comes at the expense of signal strength. In other words, shifting the signal phase provides the limited ability to point, steer or change the coverage area without physically moving the antenna 18, but at the same time significantly degrades the strength of the signal being transmitted or received. Reduced signal strength means dropped calls and reduced bandwidth (poor service coverage). This major drawback is no longer acceptable in TIC systems that are being pushed to their limits by more and more devices and more and more bandwidth requirements.